JEE 2016 :: Advanced 2016 :: Chemistry 2016

• Advanced 2016 - Physics 2016
• Advanced 2016 - Chemistry 2016
• Advanced 2016 - Mathematics 2016

The diffusion coefficient of an ideal gas is proportional to its mean free path and mean speed. The absolute temperature of an ideal gas is increased 4 times and its pressure is increased 2 times. As a result , the diffusion coefficient of this gas increases x time. The value of x is .........

Answer:

Explanation:

 (DC) Diffusion coefficient  $\propto$  $\lambda$ (means free path )  $\propto$  $U_{mean}$ , thus

  (DC) $\propto$  $\lambda$ $U_{mean}$

  but, $\lambda = \frac{RT}{\sqrt{2}N_{0}\sigma p}\Rightarrow \lambda \propto\frac{T}{p}$,

  and    $U_{mean}=\sqrt{\frac{8RT}{\pi M}}\Rightarrow U_{mean}\propto\sqrt{T}$

$\therefore$     $DC\propto \frac{(T)^{\frac{3}{2}}}{p}$

 $\frac{(DC)_{2}}{(DC)_{1}}(x)=(\frac{p_{1}}{p_{2}}) (\frac{T_{2}}{T_{1}})^{\frac{3}{2}}$

$= (\frac{p_{1}}{2p_{1}})(\frac{4T_{1}}{T_{1}})^{\frac{3}{2}}=(\frac{1}{2})(8)=4$

The possible number of geometrical isomers for the complex   

 $[CoL_{2}Cl_{2}]^{-}(L=H_{2}NCH_{2}CH_{2}O^{-})$ is (are)

Answer:

Explanation:

Ligand is   

Geometrical isomers are

The mole fraction of a solute in a solution is 0.1, At 298K , molarity of this solution is the same as its molality . Density of this solution at 298K is 2.0 g cm^-3 . The ratio of the molecular weights of the solute and solvent,  $(\frac{m_{solute}}{m_{solvent}})$ is.......

Answer:

Explanation:

 Moles of solute , $n_{1}=\frac{w_{1}}{m_{1}}$ ; Moles of solvent ,   $n_{2}=\frac{w_{2}}{m_{2}}$ 

$x_{1}$ (solute)=0.1 and   $x_{2}$ ( solvent)=0.9

$\therefore$    $\frac{x_{1}}{x_{2}}=\frac{n_{1}}{n_{2}}=\frac{w_{1}}{m_{1}}.\frac{m_{2}}{w_{2}}=\frac{1}{9}$

$Molarity=\frac{Solute(moles)}{Volume(L)}$

$=\frac{W_{1}\times 1000\times2}{m_{1}(w_{1}+w_{2})}$

 Note volume= Total mass of solution /  Density

  $=(\frac{w_{1}+w_{2}}{2})mL$

  $Molality=\frac{Solute(moles)}{Solvent(kg)}=\frac{w_{1}\times1000}{m_{1}\times w_{2}}$

 Given, Molarity=Molality

 hence,   $\frac{2000w_{1}}{m_{1}(w_{1}+w_{2})}=\frac{1000 w_{1}}{m_{1} w_{2}}$

 $\therefore$                 $\frac{w_{2}}{w_{1}+w_{2}}=\frac{1}{2}$

$\Rightarrow$    $w_{1}=w_{2}=1$

$\therefore$    $\frac{w_{1}m_{2}}{m_{1}w_{2}}=\frac{1}{9}$

$\Rightarrow$    $\frac{m_{1}(solute)}{m_{2}(solvent)}=9$

In the following monobromination reaction, the number of possible chiral product (s)  is (are ).....

Answer:

Explanation:

Given compound undergoes free-radical  bromination under given conditions, replacing H by Br

$C^{*}$ is chiral carbon.

(III)   has two chiral centres and can have two structures.

(IV)  has also two chiral centres and can have two structures,

 It has the plane of symmetry thus, achiral. Thus, chiral compounds are five. I, III-A, III-B, IV-B, V.

According to the Arrhenius equation ,

Answer:

Explanation:

Rate constant, $k= Ae^{-E_{a}/RT}$  where,

   $E_{a}$= activation energy and

   A= pre exponential factor

(a) If   $E_{a}$ is high, it means  lower value  of k hence, slow reaction . Thus incorrect.

(b) On increasing temperature, molecules  are raised to higher energy (greater than  $E_{a}$  ), hence number of collisions increases. Thus, correct

(c)  $\log k=\log A-\frac{E_{a}}{RT}$

$\Rightarrow$                         $\frac{d(\log k)}{dT}=\frac{E_{a}}{RT^{2}}$

Thus, when  $E_{a}$ is high, stronger is the temperature dependence of the rate constant. Thus, correct.

 (d)   Pre-exponential factor (A) is a measure of the rate at which collisions occur. Thus, correct.

• Advanced 2016 - Physics 2016
• Advanced 2016 - Chemistry 2016
• Advanced 2016 - Mathematics 2016